In previous studies we have found the two fatty acid chains in several diacyl compounds to exhibit both extended and folded conformations. The individual fatty acid subunits exhibited both planar and long pitched helical conformations. Some showed localized twists in the hydrocarbon chains. In these previous studies we used only one specific fatty acid. We now propose an X-ray diffraction study of these effects as a function of chain length. This new study will contribute significantly to our understanding of molecular packing and factors controlling molecular interactions. Our research will have four areas of experimental involvement: synthesis, crystallization, data acquisition and structure analysis. Analogous syntheses have been previously reported in the literature some of which we have already utilized. An adequate supply of diacyl lipids is expected to be available for crystallization. Our anticipated data acquisition and data processing needs require a flexible minicomputer system for crystal structure analysis. The diacyl compounds are structural models for important membrane phospholipids. A detailed understanding of lipid interactions in these model compounds will contribute to a better knowledge of cell membrane structure. We hope that this may in turn help clarify the role of cell membranes in cancer, cell differentiation, energy transfer, virus invasion and cell division.